Phonograph tone arm for pseudo-stereophonic sound reproduction



Jan. 28, 1958 G. A. MORRELL, JR I 2,821,578

PHONOGRAPH TONE ARM FOR PSEUDO-STEREOPHONIC SOUND REPRODUCTION FiledOct. 22, 1954 2 Sheets-Sheet 1 2a I I 21 I T I I5 g i 231,2 zzlBfiAm g 1INVENTOR ozone: ARTHJR new, JR.

BY MW I ATTORNEY Jan. 28, 1958 G A.- MORRELL, JR 2,821,578 PHONOGRAPHTONE ARM FOR PSEUDO-STEREQPHONIC SOUND R RODUCTION EP Filed Oct. 22,1954 r 2 Sheets-Sheet 2 United States Patent PHONOGRAPH TONE ARM FORPSEUDO-STEREO- PHONIC SOUND REPRODUCTION George Arthur Morrell, Jr.,Conneaut, Ohio, assignor to The Astatic Corporation, Conneaut, Ohio, :1corporation of Ohio Application October 22, 1954, Serial No. 463,947Claims. (Cl. 179-100.41)

The present invention relates to phonograph apparatus, and moreparticularly to a novel and improved tone arm assembly for incorporationwith conventional phonograph turntable apparatus whereby the sameisadapted to obtain a plurality of separate pick-up responses from aconventional recording having but a single sound track or groove.

In so-called biuaural or stereophonic sound systems it is commonpractice to employ a plurality of separate sound channels each includingseparate control means and separate speaker outlets, the latter beinglocated in spaced relation within a room or theater, for example,whereby different sounds emanate from ditferent points in the room. Thelocation of the various speakers preferably corresponds approximatelywith the location of the microphones or other devices used in therecording of the sound tracks so that a realistic three dimensionaleffect is obtained during reproduction of the sound. The presentinvention, however, contemplates the use of but a single sound track,with the employment of a novel means for obtaining a plurality oftime-displaced re-- spouses from such sound track, which responses maybe separately processed and amplified and reproduced by means ofseparate spaced speaker outlet devices whereby to obtain an ingeniousand highly realistic pseudo-stereophonic sound effect. In general, thiseifect is obtained by so processing the separate time-displacedresponses that high frequency tones are reproduced at one point whilelow frequency tones are reproduced at another point. Thus, inreproducing orchestral recordings, for example, the violins and otherhigh-toned instruments will appear to be in one area of the rooms, whilethe bass instruments will appear to be in another area, all of whichcreates a unique spatial effect to the listener.

As an overall object, the present invention seeks to provide a noveltone arm assembly for use with a conventional phonograph turntablewherein are incorporated a plurality of separate record engaging styliand pick-up cartridge assemblies arranged in a novel manner so that theplurality of styli may follow the same sound track or groove in therecording, the styli being spaced a predetermined distance, however, sothat a desired timedisplaced relationship is obtained in the stimulitaken from the recording.

In the preferred form of my invention two spaced styli and pick-upcartridges are employed to obtain two separate signals or stimuli, and Ihave found it desirable to displace these signals by approximately A ofa second. Thus, it will be readily understood that in reproducing from astandard or 78 R. P. M. recording it will be necessary that the styli bespaced to a greater extent than is required for reproduction frommicro-groove 45 or 33% R. P. M. recordings. Accordingly, it is anotherand more specific object of the invention to provide a novel tone armassembly incorporating a plurality of pickup cartridge units wherein theassembly may be readily adapted during manufacture for use in eitherstandard or micro-groove recording systems, substantially the whole ofthe assembly being of standard manufacture.

A further object of the invention resides in the provision of a noveldual stylus tone arm assembly for pseudostereophonic sound reproductionwherein novel arrangements are provided for mounting separate pick-upcartridge units in the tone arm so that the separate styli of theseparate units may properly track or follow a single groove in therecording, regardless of the position of the tone arm on the recording.

Yet another object of the invention is the provision of a tone armassembly constructed in accordance with the above stated object whereinnovel means are provided for insuring that both of a pair of separatestyli will engage the same sound track or groove when the tone arm ismoved into operative position over a record disc.

The above and other objects and advantages of the invention will becomeapparent upon full consideration of the following detailed specificationand accompanying drawing wherein are disclosed certain preferredembodiments of my invention.

In the drawing:

Figure 1 is a fragmentary longitudinal section view ofteachings" Figures4 and 5 are fragmentary longitudinal section and bottom plan viewsrespectively of a second embodiment of the tone arm of my invention; and

Figure 6 is an illustrative representation of the improved tone armassembly of my invention, showing the manner in which a plurality ofseparately mounted recorded engaging styli track a single sound grooveacross the face of a recording disc.

Referring now to the drawing, and initially to Figures 1-3 thereof, thenumeral 10 designates a tone arm member of generally conventionalconstruction, in the outer free end of which is mounted a tandem pick-upcartridge assembly 12, the latter being mounted by means or screws 14which engage threaded bosses 11 on the tone arm. in accordance with thepreferred teachings of the invention the tandem pick-up cartridgeassembly 12 comprises a fiat metal mounting plate 13 which is secureddirectly to the tone arm 10 and which mounts at its forward end portiona first pick-up cartridge 15. the latter being secured in spacedrelation to the mounting plate 13" by means of suitable screws 16 andspacing washers 17, substantially as shown in Figure 1. The cartridge15, in

the illustrated apparatus, is reversely disposed with re-l spect to thetone arm 10; that is, the stylus member 25 of the cartridge assemblyextends rearwardly from the rearward end of the cartridge. Thus, theextreme forward tip of the stylus member 25 is provided with an acutebend so that it engages the surface of a forwardly moving recording discin the proper manner. As shown in Figure 2 the mounting plate 13 extendsrearwardly considerably beyond the first pick-up cartridge 15. Andextending downwardly from the rearwardmost portion of the plate 13 is astud or pivot 18 which is threaded at its lower end to receive a nut 21.Supported on the pivot member 18 is a forwardly extending auxiliarysupporting arm 19, which is provided with a bear ing portion 19'- whichengages the pivot 18 and is supported thereon by means of afriction-reducing washer;

20 and the nut 21.

At the outer or forward end of the cartridge supporting arm 19 ismounted, ,byirneans of bolts 23, a second pick:

up cartridge 22. The second cartridge 22 faces forwardly in the main armand is provided with a conventional forwardly extending stylus member26. In the illustrated arrangement the tandem cartridge assembly isconditioned for use in the microgroove recording systems, and the styli25 and 26 are spaced about three-eighths of an inch apart so that whenboth styli track the same record groove the response of the secondstylus 26 will be advanced in time by approximately second with respectto the response of the first or forward stylus 25, it being understoodthat in normal operation the surface of a record disc will be movingfrom right to left with respect to the arm shown in Figure 1.

In accordance with the teachings of the invention the auxiliarycartridge supporting arm 19 is offset downwardly at its forward endportion so that the two cartridge assemblies and 22 are positioned onapproximately the same level. Preferably, however, the second cartridge26 should normally hang slightly lower than the first cartridge 15 sothat when the complete tandem assembly is positioned in record engagingposition the forward cartridge 15 supports little if any of, the weightof the second cartridge.22.

Of course, the cartridges 15 and 22 are of conventional design, and aretherefore intended to support the Weight of the tone arm, so that acertain predetermined stylus pressure is afforded. In the illustratedapparatus the stylus 25 of the forward cartridge supports substantiallythe entire weight of the tone arm, in accordance with the thus statedconventional practice. Accordingly, there is secured to the uppersurface of the auxiliary cartridge supporting arm 19 a small lead weight24 which serves to apply a predetermined pressure to the second stylus26, to simulate the weight of a normal tone arm. It will be understood,of course, that this weight does not substantially affect the operatingcharacteristics of the forward stylus 15 because of self-supportingnature of the second 7 cartridge assembly.

provided with output terminals 15 and 22' respectively which areseparately connected to dual conductor cables 27 and 28 respectively.The separate output responses thus obtained from the cartridges 15 and22 are preferably separately'amplified and processed and directed tospaced outlet speakers so that a unique stereophonic or binaural soundeffect is obtained. Usually it will be desirable to separately filterthe separate responses so that a first frequency band is amplified and,reproduced in one system while another frequency band is amplified andreproduced in a separate system.

Referring now to Figure 6, there is shown a conventional single-trackrecording disc 31 which, in the illustration, is of the slow speed ormicro-groove type. The disc 31 is centered upon a suitable turntable,not shown, by means of a center spindle S1. Adjacent the turntable is afixed universal pivot device 50 which supports the tone arm 10 for bothup-and-down and side-to-side movements, in the conventional manner. Inaccordance with the preferred practice followed in the art the pivotpoint 50 is so positioned, and the arm 10 so arranged that the stylus orstyli may track the record groove substantially tangentially across theentire face of the record. It will be observed, however, that as theradius of the record groove decreases toward the center of the disc therelation of the groove and the direct line (indicated at 32) between theouter or fixed stylus 25 continually changes. That is, with the stylusengaging the groove adjacent the outer edge of the record there is arelatively wide angle between groove and the direct line 32 between thestylus 25 and pivot 50, while at the inner or center portion of therecord the direct line 32 is almost tangent to the groove. Thus, inorder for the second stylus 26 to properly follow the groove it mustmove progressively .closer to the direct line-32 as the tone. arm movesinardly." Of course, as the line 32 is fixed in its relation to the tonearm 10 the stylus 26 must move with respect to the arm 10 in thedirection of the center of the record disc. In the apparatus of mypresent invention this is provided for by the pivoted mounting orsupport for the cartridge 22, all as heretofore described.

Of course, since the relation of the floating cartridge 22 to the fixedcartridge 15 will depend upon the radius of the groove at the point oftracking, there will necessarily be a variance in the initial relationof the cartridges for record discs of different sizes; and sincerecording discs are conventionally manufactured in several differentsizes I have found it necessary to provide means for adjustably locatingthe floating cartridge 22 in an initial position so that when the tonearm 10 is lowered into playing position at the outer edge of a recordingdisc both styli 25 and 26 will automatically engage with the sameconvolution of the sound track or groove. To this end I provide that thepivot stud 18 for the floating cartridge 22 be tilted or canted in themanner shown in Figure 3 so that the action of gravity upon the floatingcartridge 22' urges the same toward the outer side of the tone arm 10,or away from the line 32 shown in Figure 6. In accord= ance with theteachings of the invention there is provided on the outer wall of thetone arm 10 a threaded here which receives an adjustable thumb screw 29.Theinner end of the thumb screw 29 projects into the interior of thetone arm toward the floating cartridge 22 and defines a stop to limitthe extent of pivoting movement of the cartridge 22 in a directiontoward the outer wall of the tone arm. A lock nut 30 is also provided sothat the thumb screw may be securely locked in any of its adjustedpositions. Of course, once the tone arm is lowered into playing positionand the styli 25 and 26 begin to track a sound groove the floatingcartridge will move progressively away from the thumb screw 29 as isclearly indicated in Figure 6.

Referring again to Figure 1, I have illustrated therein an arrangementwherein the stylus 25 carried by the fixed cartridge is replaced by areversely disposedthat' is, forwardly extending-stylus member 25. Thearrangement is such that the distance between the stylus tips isconsiderably greater than in the first described apparatus,

so that when the recording disc is revolving at an increased speed, forexample the standard speed of 78 revolutions per minute, the desiredtime-displaced relationship of the separate pick-up responses ismaintained substantially constant. Of course, while I prefer that thesecond pick-up response be delayed by approximately of a in U. S. PatentNo. 2,575,999, to Cordes, are employed' In the latter embodiment thecartridge assemblies 15" and 22" are of tall, narrow physical outline,whereas in the first described embodiment the cartridge assemblies areof small vertical but relatively large transverse andlongitudinaldimensions. Thus, in the embodiment of Figures 4 and 5 the mountingplate 13 is of a slightly different form, and the stylus loading weight24 is mounted at the side of the floating cartridge 22'. In otherrespects the embodiments are the same or equivalent.

It should thus be apparent that I have accomplished the several objectsinitially set forth. The subject invention represents a substantialadvance in the phonographic art whereby it is'now possible and practicalfor home users of phonographic apparatus to obtain a unique and pleasingpseudo-stereophonic sound effect while employing conventional singletrack records. The heart of the invention resides in the provision of apractical unitary tone arm assembly incorporating a pair of pick-upcartridge units in such manner that the separate styli of the units maytrack a single sound groove in time delayed relation across the entireface of a record, notwithstanding that the radius of the groovecontinually varies, as does the orientation of the tone arm with respectto the recording disc.

Various specific features of importance are the provision of a novelfloating support for one of the tandem cartridges whereby the stylus tiploading may be properly realized, the provision of means for permittingrelative movement between the cartridges as required in properlytracking a sound groove, and the provision of readily adjustable meansfor automatically orienting the cartridges in proper initial relation sothat when the tone arm is lowered into operative engagement with arecording disc the several styli will engage the same convolution of thesound groove.

Where it is desired to employ a single stylus, for conventionalreproduction, the floating cartridge assembly may be removed orotherwise rendered inoperative; and to this end a skilled mechanic mayprovide, within the teachings of the invention, suitable means forlocking the floating cartridge assembly in raised or retracted relation.

It should thus be clearly understood that the embodiments hereinspecifically shown and described are intended to be illustrative only,as many alterations may be made therein without departing from thespirit and scope of the invention. For example, the teachings of thisinvention are clearly applicable to arrangements employing more than twopick-up units. It is therefore recommended that reference be had to thefollowing appended claims.

I claim:

1. A tandem cartridge phonograph tone arm assembly forpseudo-sterophonic sound reproduction comprising in combination a tonearm, a first pick-up cartridge assembly mounted in fixed relation tosaid tone arm, and a second pick-up cartridge mounted in floatingrelation to said tone arm, said cartridge assemblies having separatespaced stylus members arranged to track the same convolution of arecording disc sound groove in time-displaced relation whereby one ofsaid separate spaced stylus members is movable a predetermined distancefrom the other during tracking across the record disc.

2. Apparatus according to claim 1 further including means incorporatedwith said second pick-up cartridge to increase the weight thereofwhereby to simulate the weight of the unsupported free end of a tonearm.

3. Apparatus according to claim 1 further including means causing saidsecond cartridge assembly to be urged into a predetermined initialrelation with respect to said tone arm.

4. A tandem cartridge phonograph tone arm assembly forpseudo-stereophonic sound reproduction comprising in combination a tonearm, a first pick-up cartridge assembly mounted in said tone arm, and asecond pick-up cartridge mounted in said tone arm in floating relationto said first cartridge assembly, said cartridge assemblies havingseparate spaced stylus members arranged to track the same convolution ofa recording disc sound groove in time-displaced relation whereby one ofsaid separate spaced stylus members is movable a predetermined disfiancefrom the other during tracking across the record 5. A tandem cartridgephonograph tone arm assembly for pseudo-stereophonic sound reproductioncomprising in combination a tone arm, cartridge mounting means securedin said tone arm, a first pick-up cartridge mounted in fixed relation tosaid cartridge mounting means, an auxiliary cartridge supporting memberpivotally mounted 6 on said mounting means, and a second pick-upcartridge fixedly mounted on said auxiliary supporting member, saidcartridge assemblies having separate spaced stylus members arranged totrack the same convolution of a recording disc sound groove intime-displaced relation whereby one of said separate spaced stylusmembers is movable a predetermined distance from the other duringtracking across the record disc.

6. Apparatus according to claim 5 further including means carried bysaid auxiliary supporting member to add additional weight thereto.

7. A tandem cartridge phonograph tone arm assembly forpseudo-stereophonic sound reproduction comprising in combination a tonearm, a first pick-up cartridge assembly mounted in fixed relation tosaid tone arm, a second pick-up cartridge mounted in floating relationto said tone arm, said cartridge assemblies having separate spacedstylus members arranged to track the same convolution of a recordingdisc sound groove in time-displaced relation, means incorporated withsaid second pick-up cartridge to increase the weight thereof whereby tosimulate the weight of the unsupported free end of the tone arm, meanscausing said second cartridge assembly to be urged into a predeterminedinitial relation with respect to said tone arm, and adjustable limitmeans determining said initial relation.

8. A tandem cartridge phonograph tone arm assembly forpseudo-stereophonic sound reproduction comprising in combination a tonearm, a first pick-up cartridge assembly mounted in fixed relation tosaid tone arm, a second pick-up cartridge mounted in floating relationto said tone arm, said cartridge assemblies having separate spacedstylus members arranged to track the same convolution of a recordingdisc sound groove in time-displaced relation, means incorporated withsaid second pick-up cartridge to increase the weight thereof whereby tosimulate the weight of the unsupported free end of a tone arm, meanscausing said second cartridge assembly to be urged into a predeterminedinitial relation with respect to said tone arm, and said means tendingto urge comprises a canted but substantially vertical pivot means forsaid second cartridge whereby said cartridge tends to pivot in a firstdirection by the action of gravity.

9. Apparatus according to claim 8 further including an adjustableabutment member positioned at one side of said tone arm to limit thepivotal movement of said second cartridge in said first direction.

10. A tandem cartridge phonograph tone arm assembly forpseudo-stereophonic sound reproduction comprising in combination a tonearm, cartridge mounting means secured in said tone arm, a first pick-upcartridge mounted in fixed relation to said cartridge mounting means, anauxiliary cartridge supporting member pivotally mounted on said mountingmeans, a second pick-up cartridge fixedly mounted on said auxiliarysupporting member, said cartridge assemblies having separate spacedstylus members arranged to track the same convolution of a recordingdisc sound groove in time-displaced relation, said auxiliary supportingmember having a bent-around end portion defining spaced bearingportions, and a member depending from said cartridge mounting means andengaging said spaced bearing portions.

References Cited in the file of this patent UNITED STATES PATENTS1,811,841 Benjamin June 30, 1931 1,992,893 Thomas Feb. 26, 19352,079,959 Fear May 11, 1937 2,105,318 Goldsmith Ian. 11, 1938 FOREIGNPATENTS 737,328 Germany July 10, 1943

